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Biomedical subjects

E G Loten

Publications and source records attributed to E G Loten.

At least 19 recordsLinked to original sources
PubMed1999

Brief problem-solving questions in medical school examinations: is it necessary for students to explain their answers?

OBJECTIVE: To compare outcomes when answers to objective type problem-solving questions are marked with and without consideration of students' explanations of their answers. DESIGN: Students answered six multiple-part problem-solving questions on the final examination for a course in clinical biochemistry. Each part required a choice from a list, a number or a few words, plus an explanation or justification. Scores were determined independently for the answers alone and for the answers plus explanations. The outcomes of the two marking methods were compared. SETTING: Department of Pathology, University of Otago Medical School, Dunedin, New Zealand. SUBJECTS: Final year preclinical medical students. RESULTS: Marks were slightly higher for answers alone than for answers plus explanations (overall mean, 82.1%; standard deviation, 9.8% vs. 77.1%; 9.3%; P < 0.001 by paired t-test). There was a very high correlation between scores derived from the two methods (r=0. 87). Consideration of the answers alone (without explanations) was about as good as answers plus explanations in identifying students who performed at different levels overall on the examination and in identifying the weakest students. CONCLUSIONS: The data suggest that when students arrived at the correct answers, their information and reasons were usually correct and that answers alone discriminate adequately among students with different levels of knowledge and ability. By dispensing with the requirement for explanations, we would be able to ask more questions and mark objectively, so competent students should not be disadvantaged by the lack of opportunity to explain their reasoning.

Education, Medical, Undergraduate↗
PubMed1999

Curriculum reform at the University of Otago Medical School.

The University of Otago Medical School, the older of the two medical schools in New Zealand, identified during the 1980s many of the same problems with its undergraduate curriculum as were reported in the United States, Canada, and the United Kingdom. An early, overly ambitious attempt to introduce a full problem-based learning curriculum at Otago failed; however, many piecemeal changes that embodied some of the principles of problem-based learning were successfully implemented. Subsequently, as desire for more coordinated and substantive change grew, Otago's faculty used what they had learned from their first effort to successfully introduce a modular systems-based preclinical curriculum in 1997. The authors describe the features of the new curriculum and discuss two components (a systems-integration course and a large-scale program of computerized in-course testing) that are particularly innovative. The new curriculum is already achieving one of its main goals (increasing the perceived relevance of preclinical teaching) and other outcomes are being evaluated.

Academic Medical Centers↗
PubMed1997

Pilot studies of in-course assessment for a revised medical curriculum: I. Paper-based, whole class.

PURPOSE: To test a paper-based method of in-course assessment for a modular, systems-oriented medical curriculum at the University of Otago Medical School. METHOD: In 1996, 193 students took paper-based quizzes on the first four topics of a course in clinical biochemistry. A score of 75% was required for passing, but students could retake quizzes. The subsequent test on these four topics was constructed from questions used in previous years. The next four topics were taught without quizzes. The test on these topics was again constructed from questions used in past years. The authors examined the performances on the quizzes and tests and sought the students' opinions about the program. RESULTS: 72.0-95.3% of the students passed the quizzes the first time and 94.8-99.5% passed by the second version. Performance on the subsequent test items was higher than [corrected] when the items had been used previously; so was performance on three of the four questions for the next four topics, none of which had been accompanied by quizzes. Students valued the quizzes as a stimulus to study and as feedback. They preferred the segment of the course with the quizzes to the segment without them. CONCLUSION: This method of in-course assessment was easy to administer and highly acceptable to the students. Performance on the quizzes was more than satisfactory and a passing score of 75% was reasonable. Such quizzes appeared to be able to replace a test that required explanation of answers while increasing the numbers of questions that could be asked and decreasing the marking time.

Biochemistry↗
PubMed1997

Pilot studies of in-course assessment for a revised medical curriculum: II. Computer-based, individual.

PURPOSE: To test a computer-based method of in-course assessment for a modular, systems-oriented medical curriculum at the University of Otago Medical School. METHOD: For the in-course assessment in anatomic pathology, 193 students completed five biweekly (i.e., every two weeks), criterion-referenced, computer-based quizzes incorporating many digitized photographs and a variety of question formats. The students signed up to take quizzes at any of ten available times during each quiz week. A score of 70% was required for passing each quiz, but the students could retake quizzes up to two more times in alternative versions. The students' opinions about biweekly testing and computer-based testing were sought. RESULTS: All 193 students satisfactorily completed the assessment program, with no significant problems with hardware, software, or administration during the more than 1,000 computer-based quizzes. The students valued the bi-weekly quizzes as a stimulus for study and for feedback. They strongly supported computer-based quizzes, identifying a variety of benefits in their responses to the questionnaire. The staff found that development of visually rich quizzes was greatly facilitated by the use of computers. CONCLUSION: The study confirmed the feasibility of using regular, computer-based quizzes for in-course assessment of a large medical school class and demonstrated assessments of a kind that would be difficult to achieve by means other than with computers.

Computer-Assisted Instruction↗
PubMed1993

Activation and inhibition of insulin receptor autophosphorylation by trypsin treatment of intact H35 cells.

1. Treatment of intact cultured H35 cells with trypsin (1 mg/ml) for 15 min at low temperature (4 degrees C) or for 30 sec at 37 degrees C causes activation of the insulin receptor subsequently isolated from the cells. 2. Receptor activation was assessed by increased phosphotyrosine content of the beta-subunit of the receptor, and increased autophosphorylation using [32P]-ATP. 3. Treatment of the cells for 15 min at 37 degrees C however completely abolished insulin binding and all insulin receptor kinase activity. 4. These data demonstrate that proteolytic damage of the extracellular domain of the insulin receptor can render the receptor kinase inactive and lead to a cell which is unresponsive to insulin.

Adenosine Triphosphate↗
PubMed1992

Direct stimulation of immediate-early genes by intranuclear insulin in trypsin-treated H35 hepatoma cells.

H35 hepatoma cells were treated with trypsin to abolish insulin binding and insulin-stimulated receptor kinase activity. Insulin was, however, internalized by fluid-phase endocytosis in trypsin-treated cells. Furthermore, nuclear accumulation of insulin was similar in control and trypsin-treated hepatoma cells. Northern blot analysis revealed insulin increased g33 and c-fos mRNA concentrations identically in control and trypsin-treated cells but had no effect on beta 2-microglobulin mRNA. Actinomycin D treatment prior to or after insulin addition demonstrated that insulin increased gene transcription and had no effect on mRNA degradation. These studies suggest that the accumulation of intact insulin in cell nuclei may be directly involved in the increased transcription of immediate-early genes.

Cell Cycle↗
PubMed1992

Nonreceptor mediated nuclear accumulation of insulin in H35 rat hepatoma cells.

We previously demonstrated that insulin accumulated in the nucleus in several cell types and partially characterized the uptake mechanisms and pathways in H35 rat hepatoma cells. Nuclear accumulation of insulin was energy independent, time, temperature, and insulin concentration dependent, but apparently nonsaturable. This study investigated further the initial endocytotic pathways that contribute to the nuclear accumulation of insulin using trypsin treatment of the cells to prevent insulin binding to its plasma membrane receptor. Total cell-associated, intracellular, and nuclear insulin were compared in control and trypsin-treated H35 hepatoma cells. Trypsin treatment markedly decreased total cell-associated and intracellular insulin as well as the nuclear accumulation of insulin when cells were incubated with 2.8 ng/ml insulin. When the cells were incubated with 100 ng/ml insulin, trypsin treatment totally inhibited insulin binding to the plasma membrane for at least 90 min. However, intracellular accumulation of insulin was reduced by only 50% at 60 min, and trypsin treatment failed to inhibit the nuclear accumulation of insulin. Chemical extraction and Sephadex G-50 chromatography revealed nuclear associated insulin in trypsin-treated cells was identical to that in control cells incubated with either 2.8 or 100 ng/ml insulin. These results suggest that a nonreceptor mediated uptake pathway, i.e., fluid-phase endocytosis, contributed significantly to the nuclear accumulation of insulin at high insulin concentrations, but at lower insulin concentrations the receptor-mediated pathway predominated. No matter which initial endocytotic route was used to internalize insulin, the insulin apparently associated with the same nuclear matrix proteins. This association of insulin with the nuclear matrix may be involved in regulation of nuclear events such as cell growth and differentiation or gene transcription.

Animals↗
PubMed1991

Fetal lung development in rats with a glycogen storage disorder.

A New Zealand strain of rats (NZR/Mh) is unable to mobilize liver glycogen due to a deficiency of phosphorylase b kinase. Affected homozygous rats (gsd/gsd) were used to assess the developmental relationship between lung glycogen loss and surfactant phospholipid and protein biosynthesis. Phosphorylase a and phosphorylase b kinase activities were negligible in gsd/gsd fetal lungs compared with controls from gestational day (D18) until postnatal day 1 (D + 1). At D20, tissue glycogen content was 158 +/- 5 and 181 +/- 6 mumol/g lung for control and gsd/gsd, respectively. Control rats mobilized 84% of their lung glycogen by D + 1, whereas the gsd/gsd strain retained 70-80% of D19-20 levels. This apparent fall in gsd/gsd glycogen per gram lung was due to an increase in cellular protein and size. Thus, in controls, total glycogen per lung decreased 65% from D20 to D + 1, whereas DNA doubled. In contrast, gsd/gsd lung growth resulted in a doubling of total lung glycogen, whereas the glycogen-to-DNA ratio remained constant. A lack of cellular glycogenolysis was confirmed by electron microscopy where gsd/gsd type II cells remained large and glycogen-rich over the entire perinatal interval. The potential for glycogen breakdown by a lysosomal alpha-amyloglucosidase in gsd/gsd lungs was estimated in tissue homogenates, whereas rates of hydrolysis of glycogen or p-nitrophenylglucoside were significant and equal to controls at all ages tested. Incorporation of [14C]choline into phosphatidylcholine (PC) of incubated lung slices increased 1.7-fold in control lungs from D20-D21. Over the same interval, PC synthesis in gsd/gsd lungs was 40% lower and did not change.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1990

Properties and distribution of cyclic AMP phosphodiesterase from rat liver.

1. Phosphodiesterase activity in rat liver supernatant and solubilized rat liver particulate fractions was chromatographed on Q Sepharose and several characteristics of each peak determined. 2. Rat liver supernatant contained four peaks of activity. The first two of these corresponded to type I and II phosphodiesterases. The fourth peaks was similar to a type V activity and the third peak could not be definitely classified. 3. Particulate activity solubilized by mild protease treatment also contained four peaks of activity. The first two corresponded to the first two from the supernatant, the fourth was a type IV enzyme which is the insulin activated phosphodiesterase. The third peak could not be definitely characterized. 4. Particulate activity solubilised by Triton X-100 contained three peaks. Two had the properties of a type IV enzyme but only one of these was immunologically identified as the insulin sensitive enzyme. The remaining activity was similar to the chymotrypsin peak 3 activity. 5. Most of the particulate phosphodiesterase of rat liver is found in a microsomal fraction, and most is the insulin sensitive type IV enzyme.

1-Methyl-3-isobutylxanthine↗
PubMed1990

Phosphorylation of hormone sensitive phosphodiesterase in isolated adipocytes.

Cyclic AMP phosphodiesterase in rat adipocytes is stimulated by insulin and also by agents that increase cyclic AMP levels. When the enzyme is immunoprecipitated from a solubilised microsomal preparation from adipocytes prelabelled with radioactive phosphate and separated on SDS polyacrylamide gels, label is found in a protein band at the expected Mr for adipose tissue phosphodiesterase. Treatment of the adipocytes with isoproterenol or methyl isobutylxanthine increased the labelling of this band. Insulin alone had no effect on its labelling but did decrease the incorporation of label caused by isoproterenol.

1-Methyl-3-isobutylxanthine↗
PubMed1989

Insulin and lipolytic hormones stimulate the same phosphodiesterase isoform in rat adipose tissue.

Insulin sensitive phosphodiesterase from rat adipocytes is found in particulate fractions. Solubilisation of the enzyme with triton X-100 yields a preparation containing more than one phosphodiesterase activity as judged by its rate of thermal denaturation at 45 degrees C and by its non-linear kinetic plots. Immunoprecipitation of solubilised activity with a polyclonal antiserum raised against purified insulin-sensitive rat liver phosphodiesterase selected a form of the enzyme which showed a single exponential decay of enzyme activity when heated at 45 degrees C and linear low Km kinetics. Treatment of adipocytes with insulin ACTH, glucagon or isoproterenol stimulated the low Km particulate phosphodiesterase. The hormonal activation was retained following solubilisation and was also seen when activity was immunoprecipitated. It is suggested that all four hormones activate the same form of phosphodiesterase.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1988

Purification of an insulin-sensitive cyclic AMP phosphodiesterase from rat liver.

A low-Km cyclic nucleotide phosphodiesterase solubilised from rat liver membranes by mild proteolysis with chymotrypsin has been purified to apparent homogeneity. The purification included chromatography on cellulose phosphate, Ecteola-cellulose, hydroxyapatite, a theophylline affinity matrix and HPLC on a DEAE-substituted column. The purified enzyme has linear kinetic plots with a Km of 0.24 microM and a Vmax of 6.2 mumol mg-1 min-1 with cyclic AMP as a substrate. It also hydrolyses cyclic GMP with a Km of 0.17 microM and a Vmax which is about a third of that with cyclic AMP. Cyclic GMP is also a competitive inhibitor of cyclic AMP hydrolysis with a Ki of 0.18 microM. The proteolytically solubilised enzyme has a subunit molecular mass of 73 kDa by SDS gel electrophoresis and of 130 kDa by HPLC size-exclusion chromatography, suggesting that it exists as a dimer. A partially purified preparation of this enzyme was used to raise antiserum in a sheep. The antiserum immunoprecipitated activity from liver and adipose tissue of rat and mouse. It had little activity against phosphodiesterase from other rat tissues or other species. Insulin-activated phosphodiesterase from both adipocytes and hepatocytes was immunoprecipitated by the antiserum suggesting that the purified enzyme was an insulin-sensitive phosphodiesterase.

3',5'-Cyclic-AMP Phosphodiesterases↗